This invention relates to heat-exchange apparatus, and more particularly to apparatus wherein cooling water is supplied to a surface of a cooling jacket or wall. It is particularly well suited for cooling a jacket of a cooler used in the manufacture of cement, but is not limited thereto.
Coolers of the type used in the manufacture of cement have an upright tubular (cylindrical) jacket or wall. The hot cement gruel, which may have a temperature up to about 120.degree. C., is advanced along and in contact with the inner side of the jacket. To cool this gruel, hereafter called the material for convenience, cooling water is made to flow over the outer side of the jacket. Proper cooling is extremely important and it is essential that a constant film (of small thickness) of such cooling water flows over this outer side and cools all portions thereof.
If the thickness of this water film becomes too great, the danger develops that the water may lift off the jacket surface and flow in free-falling ribbons or streams. This results not only in excessive use of water but in poor cooling. On the other hand, if the film thickness is too small then the water turns to steam as it runs over the jacket; the negative effects of steam in a cement-manufacturing plant are known and need not be described here in detail. Furthermore, in this situation there is again the inevitable reduction of cooling capacity when areas of the jacket surface become dry due to the steam formation.
In coolers of the type which is being described here it is, therefore, extremely important to assure that the cooling water flows over the cooling jacket in form of a continuous film of substantially uniform thickness, which film must be present over the entire circumference of the jacket; splashing, free-falling or flashing of the water into steam must be avoided.
In the prior art it has been proposed to surround the jacket with an annular water trough from which the water runs onto an annular, downwardly inclined guide baffle. A free edge of the baffle defines with the jacket a narrow annular gap through which the water runs. However, the cooperating parts (i.e. the baffle and the jacket) are sheet-metal elements which are not (and are not intended to be) manufactured to particularly close tolerances; to do so would make them uneconomically expensive. Due to this tolerance problem neither the baffle nor the jacket are completely round; the width of the gap therefore varies over the gap circumference and, as a consequence, the thickness of the water film is not uniform everywhere. The above-discussed disadvantages are therefore not effectively avoided. A proposal has been made to install thin metal lips in the gap in order to avoid "sheeting" of the water, i.e. free fall out of contact with the jacket; however, this is not particularly effective and, moreover, whenever a foreign body (e.g. dirt, mineral deposit which breaks off the trough) enters the gap, it immediately serves to direct the water away from the jacket and to cause sheeting.
Another proposal involves the use of a pressurized water container having an outlet gap which is closed by a lip-shaped rubber seal. Under the pressure of water in the container the seal is deflected and permits the outflow of a certain quantity of water onto the jacket per unit time. This arrangement, also, fails to avoid the formation of steam and does not ensure uniform distribution of the cooling water about the jacket in form of a water film.